1. Field of the Invention
The present invention pertains to optoelectronic devices or optical subassemblies. The invention more particularly concerns a small format optoelectronic package.
2. Discussion of the Background
Optoelectronic devices such as optical transceivers are known in the art and include active optical devices or diode packages. Common diode packages include LED packages such as a TO-46 package or a 5.6 mm TO style laser diode package such as an RLD-85PC diode package by Rohm, Incorporated. These diode packages or TO cans typically include a metallic housing having a laser diode or LED for transmitting data and a photo diode for performing power-monitoring, metal contact leads exiting from the diodes for connection to a power source and a cover glass opposed to the diode, through which the energy is transmitted. Discussion of the power-monitoring and feedback control of the laser diode by the photo diode is presented in U.S. Pat. Nos. 5,812,582 and 5,815,623. U.S. Pat. Nos. 5,812,582 and 5,815,623 are hereby incorporated herein by reference. The TO can is hermetically sealed. Often, optics housings are metallic so as to provide ruggedness, ease of machining complicated shapes, and to enhance shielding of electromagnetic fields.
Smaller optoelectronic packages allow the devices into which the optoelectronic packages are placed to become smaller. Smaller optoelectronic packages allow for a higher density of data transmission in a given space. Currently, there is a great demand for smaller optoelectronic packages.
FIG. 8 is a partial cross-sectional pictorial view of an optoelectronic package 200. The optoelectronic package 200 includes a base element 212, posts 206, 208, 210, extending through the base element 212 and secured thereto with solidified molten glass 214, a monitor diode 204 mounted on the base element 212, an optical emitting element 202 mounted on the monitor diode 204, a can 218 and lens 216 enclosing the monitor diode 204 and the optical emitting element 202. In an effort to reduce space, the optical emitting element 202 is mounted on top of the monitor diode 204. Electrically conductive posts 206, 208, 210 extend through through-holes in the electrically conductive base element 212. The posts 206, 208, 210 are electrically insulated from the base element 212 by solidified molten glass 214 which also attaches the posts 206, 208, 210 to the base element 212. The posts 206, 208, 210 are large as compared to the other components and require a large area for their mounting and placement.
At minimum, the diameter across the base element 212 is approximately 3.8 millimeters, as incorporated on the SLT2160-LN series of transmitter optical sub-assemblies manufactured by Sumitomo Electric Industries, Ltd. Thus, if two of these devices are placed side-by-side, on the same plane, the distance between the optical axes is, hypothetically, at best, 3.8 millimeters. However, typically, the optical axes are separated by 6.25 millimeters, due to packaging constraints as in typical LC duplex transceivers such as Methode Electronics, Inc.""s, part number MLC-25-4-X-TL which is described in the data sheet entitled, xe2x80x9cMLC-25-4-X-TL Optical Gigabit Ethernet xe2x80x94+3.3V Small Form Factor (SFF) Transceiverxe2x80x941.25 GBaud.xe2x80x9d
Therefore, there is a need in the industry for a small format optoelectronic package that has a small diameter and is easy to manufacture. Furthermore, there is a need for an optoelectronic package that can be placed adjacent to another optoelectronic package.
Therefore, it is an object of the present invention to provide a small format optoelectronic device.
It is still another object of the invention to provide a small format optoelectronic device which is hermetically sealed and economical to manufacture.
Yet another object of the invention is to provide a small format optoelectronic device which is able to be placed adjacent to another small format optoelectronic device.
It is a further object of the invention to provide a small format optoelectronic device which is easy to install, and provides for more efficient utilization of the limited surface area by incorporating rectangular geometry.
In one form of the invention, the small format optoelectronic package or device includes a non-electrically conductive substrate partially covered by an electrically conductive can. The electrically conductive can has a transparent element affixed to an aperture of the electrically conductive can. The electrically conductive can encloses and hermetically seals an optical diode between the electrically conductive can and the non-electrically conductive substrate. The non-electrically conductive substrate has two through-holes formed through a thickness of the non-electrically conductive substrate. The two through-holes are filled with an electrically conductive material so as to form two electrically conductive vias. When co-fired with the substrate, the electrically conductive vias form a hermetic seal. Additionally, a surface of the non-electrically conductive substrate is organized into three regions. The third region has the electrically conductive plating material applied thereto. The first through-hole protrudes through the first region. The second through-hole protrudes through the second region. The first region has a first surface. The second region has a second surface. The first surface is at a different elevation than the second surface. The optical diode has a first lead or contact electrically connected to the first via, and the optical diode has a second lead electrically connected to the second via. The optical diode has a third surface, where the third surface is substantially coplanar with the second surface.
In another form of the invention, the small format optoelectronic package or device includes a non-electrically conductive substrate partially covered by an electrically conductive can. The electrically conductive can has a transparent element affixed to an aperture of the electrically conductive can. The electrically conductive can encloses and hermetically seals an optical diode between the electrically conductive can and the non-electrically conductive substrate. The non-electrically conductive substrate has two through-holes formed through a thickness of the non-electrically conductive substrate. The two through-holes are filled with an electrically conductive material so as to form two electrically conductive vias. When co-fired with the substrate, the electrically conductive vias form a hermetic seal. Additionally, a surface of the non-electrically conductive substrate is organized into two regions. The second region has the electrically conductive plating material applied thereto. The first through-hole protrudes through the first region. The second through-hole protrudes through the first region. The optical diode has a first lead and a second lead. The first lead of the optical diode electrically connected to the first conductive via. A flex connector has a conductive trace. The conductive trace of the flex connector electrically connects the second lead of the optical diode to the second conductive via.
In yet another form of the invention, the small format optoelectronic package or device includes a non-electrically conductive substrate partially covered by an electrically conductive can. The electrically conductive can has a transparent element affixed to an aperture of the electrically conductive can. The electrically conductive can encloses and hermetically seals an optical diode between the electrically conductive can and the non-electrically conductive substrate. The non-electrically conductive substrate has two through-holes formed through a thickness of the non-electrically conductive substrate. The two through-holes are filled with an electrically conductive material so as to form two electrically conductive vias. When co-fired with the substrate, the electrically conductive vias form a hermetic seal. Additionally, a surface of the non-electrically conductive substrate is organized into two regions. The second region has the electrically conductive plating material applied thereto. The first through-hole protrudes through the first region. The second through-hole protrudes through the first region. The optical diode has a first lead and a second lead. The first lead being electrically connected to the first conductive via. The second lead being electrically connected to the second conductive via. The optical diode is a flip-chip optical diode, where both the first lead and the second lead are positioned on one side of the optical diode. Solder balls electrically connect the leads to the vias. The optical signal emanates or alternatively is received from a surface of the optical diode which is opposite to the surface that contains the leads.
Thus, the device of the invention is superior to existing optoelectronic devices. The small format optoelectronic package of the invention eliminates the use of large and bulky components, and replaces them with smaller components through use of a unique combination of materials and arrangement of the materials. Thus, the device of the invention is smaller than the prior art device.